Generic ground milling machines include a machine frame, several crawler tracks, a drive motor which usually is a combustion engine, for example, a diesel engine, a work device, in particular a milling drum housing comprising a milling drum, and frequently also a discharge conveyor for transporting the milled material. Generic ground milling machines are known, for example, from EP 24 23 384 A2 for a stabilizer/recycler, and from DE 10 2010 014 529 A1 for a road milling machine.
The milling drums each are equipped with a plurality of chiseling devices which, in addition to a work tool, in particular may comprise a chisel as well as a chisel holder and/or quick-change tool holder systems. Due to a rotational movement of the milling drum, these chiseling devices will be driven into the ground during the working operation, and thereby cause the milling of the ground substrate. The processed grounds, according to the field of application of the ground milling machine, for example, can be road surfaces, stone grounds, forestal or earth grounds, etc.
Depending on the hardness of the processed ground, considerable stress on the chiseling devices may result. Due to the continuous stress on the chiseling devices, in particular on the chisel and the chisel holder, they are particularly subjected to substantial wear on heavily stressed parts. Thus, preferably, at least parts, or components, of worn-out chiseling devices will be replaced at a certain extent of wear to maintain both the performance of the ground milling machine and the quality of the milling outcome, as well as to avoid damage on other machine components such as the milling drum.
Up to now, the time point for replacing the chiseling devices usually is determined by the operator of the ground milling machine in that the operation is interrupted, the drive motor of the milling drum is deactivated and optionally uncoupled, and the chiseling devices will be checked for wear by visual inspection. This manner of checking wear, however, is time consuming, labor-intensive and, in addition, depends on a subjective assessment of the condition of the chiseling devices.
To facilitate and objectify the assessment of wear on the chiseling devices, in the prior art, furthermore, methods are known which measure the condition of the chiseling devices via sensors, and thus permit an operator-independent assessment of the degree of wear on the chiseling devices. Such a method is known, for example, from EP 2 161 375 A2, the disclosure of which is hereby incorporated by reference in its entirety. Therein, options are described to determine the position of one or more points on the surface of a chiseling device via a sensor system. In this manner, an unbiased quantification of the degree of wear on the chiseling devices can be performed. However, in the said document, for this purpose a fixed sensor is used which is to detect, from its fixed position, all chiseling devices over the entire milling drum width. In the case of a wide to very wide milling drum, it can be necessary to use several sensors which augments the production cost of the system considerably.
However, even when using a system comprising several sensors, variations in the results arise at the edge of the respective measuring range due to the different angles between the sensor and the chiseling devices. Owing to the unequal placement of the respective chiseling devices relative to the sensor, the degree of wear on various chiseling devices is detected with varying accuracy. With a different stress on individual chiseling devices, especially, significant differences in the assessment of the condition of the chiseling devices may result for this reason.